A belligerent letter from Pyongyang was behind U.S. President Donald Trump's decision to scrap talks between his secretary of state and North Korea, according to the Washington Post. Mike Pompeo was due to make his fourth visit to North Korea this year for nuclear negotiations, but a day after being announced the trip was abruptly cancelled.

It was an angry letter from Pyongyang that was behind the decision to cancel U.S. Secretary of State Mike Pompeo's visit to North Korea. That's according to the Washington Post, which quoted unnamed senior U.S. officials.

The newspaper said the letter was sent by Kim Yong Chol, a senior official from North Korea's ruling Workers Party who led previous rounds of talks with Pompeo. So far, no details on exactly what the letter said.

But The Post reported that it was belligerent enough to convince Pompeo and President Donald Trump to cancel the trip.

The Secretary of State was planning his fourth trip this year, aimed at convincing North Korea to scrap its nuclear weapons program. But just a day after the visit was announced, Trump abruptly tweeted that it had been called off.

The president blamed the cancellation on a lack of progress "with respect to the denuclearization of the Korean Peninsula". He also said China was refusing to help out because of trade tension between Washington and Beijing.

It was the first time the president publicly admitted that his strategy to get North Korea to denuclearize might not be going according to plan. The President has pushed for negotiations in spite of resistance from some of his own advisors.

According to some U.S. intelligence and defense officials, North Korea doesn't seem ready to give up its nuclear weapons anytime soon and Pompeo's trip was unlikely to bear fruit. (Reuters)